An embedded network architecture with critical applications on an inter-node communication platform typically needs a commensurate level of fault tolerance. One approach to provide fault tolerance is by using a dual redundant network, where inter-node communication on the network can be provided using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite. Ethernet is commonly used as the local area network (LAN) protocol used for interconnecting embedded device nodes. Redundant Media Access Control (MAC) bridges, such as Ethernet switches, can be employed to facilitate multiple inter-node paths.
This solution is appropriate when there is only a single instance of each node and such nodes will utilize two network ports. For each of these nodes, one of the two ports will be connected to a primary bridge and the other will be connected to a secondary bridge. Hence, the network topology is dual redundant, providing redundant paths between any pair of dual ported nodes. Other solutions for redundant networking, such as heartbeat and token ring type schemes, require features that are not readily available on embedded network devices and/or are not transparent to the application.
Rapid spanning tree protocol (RSTP), as defined in the IEEE Standard 802.1w, is a MAC bridge (i.e., IEEE 802.1D) based protocol and is a widely accepted feature supported on most embedded Ethernet switches. RSTP is typically enabled on interconnected bridges to preclude the existence of network loops that could result in broadcast storms and also provides path redundancy.